code: use config macro

Macro is much easier to use and more readable

app/window/mainwindow/mainmenu.cpp

@@ -381,7 +381,7 @@ void MainMenu::ToolsMenuAboutToShow()
 
 void MainMenu::PlaybackMenuAboutToShow()
 {
-  playback_loop_item_->setChecked(Config::Current()["Loop"].toBool());
+  playback_loop_item_->setChecked(OLIVE_CONFIG("Loop").toBool());
 }
 
 void MainMenu::SequenceMenuAboutToShow()
@@ -506,7 +506,7 @@ void MainMenu::PlayInToOutTriggered()
 
 void MainMenu::LoopTriggered(bool enabled)
 {
-  Config::Current()["Loop"] = enabled;
+  OLIVE_CONFIG("Loop") = enabled;
 }
 
 void MainMenu::NextFrameTriggered()

app/window/mainwindow/mainwindow.cpp

@@ -473,7 +473,7 @@ void MainWindow::TimelinePanelSelectionChanged(const QVector<Block *> &blocks)
 
 void MainWindow::ShowWelcomeDialog()
 {
-  if (Config::Current()[QStringLiteral("ShowWelcomeDialog")].toBool()) {
+  if (OLIVE_CONFIG("ShowWelcomeDialog").toBool()) {
     AboutDialog ad(true, this);
     ad.exec();
   }